Status of the SP8GDH experiment

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Status of the SP8-GDH experiment
2005.Oct.6 _at_QPAC at RCNP

• Yamagata University
• Takahiro Iwata
• On behalf of the SP8-GDH collaboration

• SP8-GDH proposal
• Introduction of GDH sum rule
• Status of the world data
• Status of the SP8-GDH experiment
• PT, IGD, ID, GD,

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Proposal GDH experiment at SPring-8

• Study of the GDH sum rule for proton
  (measurement of helicity dependent
  photo-absorption cross-sections)
• Energy region 1.8 2.4 GeV 2.3 2.8 GeV
• Circularly polarized gamma beam
• Polarized polyethylene target
• 4p-detector system
• 1st double polarization experiment at SPring-8
• Approved in Oct. 2001 (QPAC )
• Status in preparation

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SP8-GDH collaboration

• Yamagata Univ. T.Iwata, H.Yoshida, Y.Tajima,
  S.Kato
• Miyazaki Univ. T.Mastuda, Y.Toi
• KEK S.Ishimoto
• SPring-8 Y.Ohashi
• Chubu Univ. N.Horikawa,
• Tohoku Univ. H.Shimizu, T.Ishikawa
• Melbourne Univ. M.Thompson, R.Rassool
• Royal Melbourne Institute of Technology M.Geso
• UCLA G.Igo, O.Tsai, C.Witten, S.Trentalange,
  V.Ghazikanian
• Bochum Univ. G.Reicherz, W.Meyer
• CUA F.Klein

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GDH sum rule

• Gerasimov-Drell-Hearn sum rule

-
Circularly polarized gamma polarized nucleon
target
Anomalous Magnetic Moment (static property)

• S.B.Gerasimov
• Yad.Fiz. 2 (1965) 598 /
• Sov. J. Nucl. Phys. 2, 430(1966)
• S.D.Drell and A.C.Hearn
• Phys.Rev. Lett. 16, 430 (1966)
• M.Hosoda and K.Yamamoto
• Prog. Theor Phys. 36 (1966) No.2,
• Lett. to Editor 425

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Derivation
ASSUMPTION spin flip amplitude vanishes at
infinite energy
General Principles Lorenz invariance, gauge
invariance, causality, relativity, crossing
symmetry, analytic amplitude
Similar sum rules are formulated for any
particles having non-zero spin ! Universal sum
rule
GDH sum rule
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GDH for proton
Running GDH integral
MAMI(Mainz)
GDH sum rule
ELSA(Bonn)
The running GDH integral overshoots the GDH
prediction at 2.9 GeV by 10.
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High-energy contribution
High-energy behavior evaluated by fitting DIS
data with Regge parameterizations
Extrapolation to high energy is good?
SP8

• Contribution above 2.9 GeV
• Bianchi and Thomas -14mb
• Simula et al. -13mb
• Total integral

GDH sum rule
If the evaluations are correct, the sum rule is
verified at 10 level.
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GDH for neutron

• Data analyses in resonance region give contrary
  results to GDH s.r.
• Interesting to see neutron GDH

phenomenological analyses with real photon data
in resonance region
phenomenological Regge approach
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Data of neutron GDH

• preliminary Mainz data ( lt 800 MeV)
• published Bonn data up to 1.8GeV
• large errors compared with proton data
• no data above 1.8 GeV

neutron
neutron
SP8
Mainz data O. Jahn, Proc.GDH2004
Bonn dataPRL 94,162001(2005)
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Objectives of SP8-GDH experiment

• Measurements of Ds for proton
• in the energy range of 1.8-2.8 GeV
• with high precision and finer energy binning
• confirmation of ELSA data ( with different
  technique)
• study extrapolation to high energy
• Prospects
• double pol. measurements in exclusive channels
• ( PTTPCLEPS configuration )
• resonance studies with double polarization
  technique
• new GDH data for neutron with pol.d target
• new proposal to be submitted
• spin study of q

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SP8-GDH Setup
Forward Detector (FD) TOF wall
Large Angle Detector(LAD)
geometrical acceptance 97 of 4p
Polarized Target(PT)
Gas Cerenkov(GC)
Inner Detector (ID)
Gamma beam
Forward Gamma Detector(FG) lead-glass PWO
PT-Magnet
Large Angle Gamma Detector (LAG) lead-plastic
Inner Gamma Detector (IGD)
1 m
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Layout of experiment
responsibility
Polarized target
PT Yamagata Bochum IGD UCLA ID
Melbourne LAD Yamagata LAG Yamagata GC
Miyazaki FD Yamagata FG TohokuYamagata DAQ
Yamagata
beam
Magnet for pol. target
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Polarized target

• Modification of
• KEK-cryostat ongoing

microwave cavity
outer pipe of the final HE

• Most parts ready
• except MC, waveguide

modified part

• a few steps for
• final assembly

still

• NMR for pol. monitor made by Bochum

beam pipe final heat exchangers walls
final heat exchanger
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Cryogenics system for polarized target at
SPring-8
2500
400
400
300
JIS250
1000
2000
2000
He3
1000
2000
200
500
500
2000
200
He3 pump system
He4 pump system
EXP. hatch
3300
He4
2000
JIS250
300
JIS65
pipe d267.4 flange d350
pipe d76.3
200
500
JIS250
JIS65
300
G.V.
JIS150
500
DN160
flange O.D.285
G.V.
EH1200
DN160
100L Dewar
200L Dewar
PT
RSV2000
EH500
1400
R601
EH80
H2060
2500
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Inner Gamma Detector (IGD)
26 layers of 5mm thick scintillators and
1.2mm thick lead sheets
Designed and RD by UCLA
Avalanche Photodiode readout 1 APD/segment
Budget application to DOE (280k)
10 MeV equiv. light output
O.Tsai(UCLA) invited to Yamagata by JSPS for 10
month( from Nov. 2005)
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Inner Detector (ID)

• Charged particle detection
• tile scintillators 25mm thick
• 10 segments x 8 sectors
• 80 tiles in total
• neighboring segments rotated by half a sector
• Readout WLS fiber(d1mm)
• clear fiber(3m long)
• 4-dimensional readout(32ch)
• Multi-anode-PMT(16ch)
• Melbourne group made preliminary study
• tiles to be made at Melbourne workshop

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Gas Cherenkov Counter
Miyazaki Univ. group in charge
Electron rejection CO2 gas at 1 bar
Gas box constructed leak check OK.
Mirror design ongoing
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Other detectors

• LAD (charged particle detection)
• scintillator plate 20mm thick , 4 PMTs
• LAG ( gamma detection)
• scintillator lead, WLS readout, 10 PMTs
• FD (charged particle detection)
• TOF wall (LEPS)
• FG ( gamma detection)
• scintillator lead, WLS readout, 20 PMTs
• (or lead glass blocks borrowed from KEK)
• PWO(LEPS)

Realistic design should be started soon
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Summary

• Proton GDH
• It is verified at 10 level at Mainz and Bonn
• Confirmation of the data is necessary
• Extrapolation to high energy is important
• Neutron GDH
• No data is available above 1.8GeV
• SP8-GDH experiment can provide additional data
  for proton and new data for neutron
• Preparation of SP8-GDH
• A few steps for completion of PT
• Work for cryogenics system at SPring-8
• Preparations of IGD, ID, GC are on the track
• Others should be started.
• Funding is required for construction,
  installation and running
• But , it is not reserved, yet.

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GDH activities in the world
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Contributions from partial channels
Q.Zhao, J.Al-Khalili and C.Bennhold (th-nucl
0201002v2)
quark model approach
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Double polarized data for exclusive
channels (Mainz data for eta p channel)
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PTTPC
LEPS spectrometer
Forward Detector (TOF wall)
Gas Cerenkov
TPC
80 mm
Gamma beam
TPC
PT-Magnet
Forward Gamma Detector (lead-glass, PWO)
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PT-Magnet
Superconducting Solenoid B2.5T(max2.6T) DB/B130
ppm (f20x50mm) warm bore 60cm length
100cm cooled by cryocooler (GM-refrigerator) ? no
need of liq. He
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Comparison between ELSA and SPring-8